Summary of JavaScript operators_javascript skills-JS Tutorial-php.cn

Summary of JavaScript operators_javascript skills

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Release： 2016-05-16 15:56:53

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In JavaScript, common operators include arithmetic operators, comparison operators and logical operators.

Table 1 JavaScript common operators

算数运算符	说明	举例	结果
=	赋值运算符。将运算符右边变量的值赋给左边变量。	x = 5 ;	-
	加号。将两个数据相加。	y=1 2;	y=3
-	减号。将两个数据相减。	z = x-y;	z=2
*	乘号。将两个数据相乘。	a=x*y;	a=15
/	除号。将两个数据相除。	b=x/z;	b=2.5
%	求余运算。求两个数据相除的余数。	c=x%z;	c=1
	自加。将操作数加1。	m= x;	m=6 x=6
--	自减。将操作数减1。	n=--x;	n=5 x=5
比较运算符	说明	举例	结果
==	相等。若两数据相等，返回 true，否则返回 false。	boolean1=(x==5);	boolean1=true
!=	不相等。若两数据不相等，返回 true，否则返回 false。	boolean2=(x!=5);	boolean2=false;
>	大于。若左边数据大于右边数据，返回 true，否则返回 false。	boolean4=(x>y);	boolean4=true
<	小于。若左边数据小于右边数据，则返回布尔值true，否则返回false。	boolean5=(x	boolean5=false
>=	大于等于。若左边数据大于或等于右边数据，返回 true，否则返回 false。	boolean6=(x>=y);	boolean6=true
<=	小于等于。若左边数据小于或等于右边数据，返回 true，否则返回 false。	boolean7=(x<=y);	boolean7=false
逻辑运算符	说明	举例	结果
&&	逻辑与。如果符号两边的操作数为真，返回true，否则返回false。	boolean_a=true&&false;	boolean_a=false
\|\|	逻辑或。如果符号两边的操作数为假，返回false，否则返回true。	boolean_b=true\|\|false;	boolean_b=true
!	逻辑非。如果符号右边的操作数为真，返回false，否则返回true。	boolean_c=!true;	boolean_c=false

" " can also be used to concatenate strings

The " " sign can not only add two data, but can also be used to connect strings.

For example:

Copy code The code is as follows:

var name=" Tom ";

var age=22;

var person="My name is " name " ! I'm " age " ! ";

alert(person);

Save and run the code to display My name is Tom ! I'm 22 !

In the above example, there are strings and values. When strings and numerical values are mixed, JavaScript will automatically determine the function of the " " sign, whether it is an addition operation or a concatenation of strings. If concatenating strings, the numeric value will also be converted to a string.

Discussion on self-increment ( ) and self-decrement (--)

It is worth noting that the self-increment ( ) and self-decrement (--) operators have different meanings when placed before and after the operand. Put it in front of the operand (front self-increment/front self-decrement), first add 1 (subtract 1) to the operand, and then perform the operation; place it after the operand (last self-increment/last self-decrement), perform the operation first, Then add 1 to the operand (decrease 1).

For example:

Copy code The code is as follows:

Display the value of y

Show the value of z

Display the value of m

Show the value of n

Save and run the code, click on the four pieces of text in sequence, and they will all display 6.

Analysis:

For y , the value of x (x=5) plus 1 becomes 6 , and then the value of x is passed to y .
For z , first pass the value of x (x=6) to z , then add 1 to x , so the value becomes 7.
For m , the value of x (x=7) minus 1 is 6, and the value of x is passed to m .
For n , first pass the value of x (x=6) to n , then subtract 1 from x , so the value becomes 5 .

Abbreviation for arithmetic operator

In order to facilitate operation and reduce code writing, JavaScript also supports the abbreviations of common mathematical operators.

Table 2 Abbreviations of common arithmetic operators

Operator

Example

Equivalent to

x =y

x=x y

x-=y

x=x-y

x*=y

x=x*y